Bulger, 83, is accused of playing a role in 19 killings during the 1970s and '80s as leader of the Winter Hill Gang, Boston's murderous Irish mob. He was captured in Santa Monica, Calif., in 2011 after 16 years as one of the nation's most wanted fugitives.

On Thursday, Judge Denise Casper gave jurors an added instruction at the request of prosecutors, urging them to make findings on each of the 33 racketeering acts against Bulger.

The 33 acts, which underpin a racketeering charge against Bulger, include the 19 killings Bulger is accused of playing a role in, plus extortions, money-laundering and narcotics distribution.

Casper told the jury that in order to find that a certain racketeering act has been proven or not proven by prosecutors, the jury must be unanimous. She said if they are unable to agree unanimously, they can move on to the next act. But she also said told them they "have a duty to attempt to reach agreement on each of the racketeering acts if you can do so conscientiously."

The added instruction appeared to be aimed at encouraging the jury to make findings on each of the murders. Relatives of the victims have sought justice for decades, and many of them have been in court for every day of the two-month trial.

Later Thursday, jurors asked to examine a machine gun that was among a cache of weapons Bulger allegedly hid in South Boston.

The 9 mm German MP40 submachine gun is the subject of the final charge of the indictment against Bulger. In that count, he is charged with possession of a firearm with an obliterated serial number. The judge agreed to send the gun in to the jury room.

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